Query Model Characteristics

How to query model characteristics such as stability,
time domain, and number of inputs and outputs.

Query Model Dynamics

This example shows how to query model dynamics such as stability,
time domain, and model order. You can use the techniques of this example
on type of model.

Load a saved state-space model.

load queryexample.mat T;

Query whether T has stable dynamics.

isstable(T)

The isstable command
returns a Boolean value of 1 (true) if all system
poles are in the open left-half plane (for continuous-time models)
or inside the open unit disk (for discrete-time models). Otherwise, isstable returns 0 (false).

Query whether T has any time delays.

hasdelay(T)

This command returns 1, which indicates that T has
a time delay. For a state-space model, time delay can be stored as
input delay, output delay, or internal delay. Use get(T) to
determine which properties of T hold the time delay.

Query whether T is proper.

isproper(T)

This command returns 1, if the system has
relative degree ≤ 0.

Query the order of T.

order(T)

For a state-space model, order returns the
number of states. For a tf or zpk model,
the order is the number of states required for a state-space realization
of the system.

Query whether T is a discrete-time
model.

isdt(T)

This command returns 1, indicating that T is
a discrete-time model. Similarly, you can use isct to query whether T is
a continuous-time model.

Query Array Size

This example shows how to query the size of model arrays, including
the number of inputs and outputs and the number of models in an array.

You can also use these commands on individual models.

Load a saved model array.

load queryexample sysarr

Query the array dimensions.

size(sysarr)

This command displays the array size, and the number of inputs,
outputs, and states of the models in the array.

Alternatively, to obtain the array dimensions as a numeric array,
use size with an output argument.

dims = size(sysarr)

This command produces the result:

dims =
3 1 2 4

The first two entries 3,1 are the number
of outputs and inputs, respectively. The remaining entries 2,4 are
the array dimensions.